1. Field of the Disclosure
The present disclosure relates to a surgical robotic system comprising a robotic arm with an end effector attached thereon.
2. Discussion of the Background Art
In the field of minimal-invasive surgery, use is made of surgical robots as surgical instruments for performing e.g. gripping and cutting processes in the patient's body. For this purpose, a surgical robotic system comprises a robotic arm and, at the end of the robotic arm, an end effector including a movable end effector element. Said end effector element can be e.g. a forceps or a pair of scissors. On the end effector, an actuator is provided for moving the end effector element such as, e.g., an arm of a forceps.
Arranged between the end effector and the robotic arm is a force sensor for detection of the forces externally acting on the end effector, particularly of the gripping forces and the contact forces. Gripping forces are defined as the forces which are generated when the end effector is gripping an object which is not in contact with its environment. Contact forces are the forces generated by the contact between the end effector or a gripped object and the environment.
The force sensor arranged between the robotic arm and the end effector serves for detecting the forces generated by indirect or direct contact between the end effector and its environment. The gripping forces can be detected by detection of the closing and respectively gripping forces exerted by the actuator.
Surgical robotic systems of the minimal-invasive type are, at least in their invasive parts, considerably miniaturized under the mechanical aspect. In presently known surgical robotic systems, the actuators are realized as Bowden cables. The Bowden cables are occasionally required to transmit considerable pulling and pushing forces. Even in cases of a highly sophisticated construction, the driving forces transmitted by the Bowden cables will at least partially interfere with the contact forces. The reason for this effect resides, inter alia, in that the occurrence of axial pulling or pushing forces will inevitably cause a stretching or shortening of the sheath of the Bowden cable, with the unavoidable consequence that undesired driving forces are inserted into the end effector.
Due to manufacturing tolerances and due to the properties of the materials used in miniaturized mechanics, a friction- and loss-free transmission of forces, e.g. via Bowden cables, cannot be guaranteed anymore or can at best be guaranteed only with considerable difficulties. In larger gripping devices, by contrast, manufacturing tolerances and material properties do not cause a problem of the above kind; thus, larger gripping devices do allow for a substantially friction- and loss-free transmission of forces. Consequently, in larger gripping devices as used e.g. in industrial applications, the extent of mutual interference between driving forces transmitted by Bowden cables or other mechanical transmission devices will be lower or even negligible.
Further, concerning the mechanical transmission of the driving forces, production and assembly of the mechanics are getting increasingly difficult and complex because of the continuing progress in miniaturization.
In view of the above, it is an object of the present invention to provide a surgical robotic system wherein the detection of the contact force is improved.